1. Field of the Invention
The present invention relates to a coating composition that includes a non-pigmentary anti-corrosive agent which protects a surface from corrosion and to a process of using the composition.
2. Description of the Prior Art
It is known in the art to provide materials in coating compositions which impart corrosion resistance to surfaces coated by the compositions. For example, in U.S. Pat. No. 3,846,148, there is disclosed composite pigments which are stated as having excellent corrosion inhibition and tannin absorptive properties. The composite pigments comprise an inert silicate mineral base pigment having adhered to the particles thereof and in intimate association therewith at least one additive compound which may be a basic or hydrated metal phosphate, phosphite, borate or chromate.
A different type of corrosion inhibiting pigment which may be used in an anti-corrosion paint is that set forth in U.S. Pat. No. 4,140,538. This type of pigment comprises about 50 to 70 mole % of an oxide of at least one metal selected from the group consisting of magnesium, calcium and zinc, about 70 to 30 mole % of Fe.sub.2 O.sub.3 and up to 20 mole % of Cr.sub.2 O.sub.3 and is formed by calcining the metal-containing compounds of materials yielding the metal oxides on calcination. Other illustrations of iron oxide-based anti-corrosive pigments may be found in U.S. Pat. No. 3,904,421, German Pat. Nos. 2,560,072, 2,560,073, 2,642,049 and 2,815,306 and Japanese Kokai Nos. 49-93414, 49-100107 and 50-12600.
Anti-corrosion pigments are also described in U.S. Pat. No. 4,156,613. The pigments are comprised of:
(a) about 30 to 70 mole percent of at least one of MgO, ZnO and CaO, and
(b) about 70 to 30 mole percent of Me.sub.2 O.sub.3 wherein Me.sub.2 O.sub.3 has the approximate molar percent composition Fe.sub.2 O.sub.3 0-100 mole %, Al.sub.2 O.sub.3 +Mn.sub.2 O.sub.3 0-100% and Cr.sub.2 O.sub.3 0-20 mole %.
An anti-corrosion paint is described in French Pat. No. 2,475,565. The paint contains 15 parts MgO with 100 parts of a 15% aqueous dispersion of polybutadiene as the active agents.
An indoor/outdoor wallpaint is described in French Pat. No. 1,506,784. The wallpaint contains carbon dioxide-free dolomite, silica gel, magnesium oxide and sodium chloride.
While unrelated to coating compositions, U.S. Pat. No. 4,360,624 describes a calcined solid solution of zinc oxide and magnesium oxide and/or calcium oxide which is added to a plastic composition as a smoke and/or fire retardent agent.